The present invention is directed to communication devices, and more particularly, to a retractable antennas suitable for use with portable devices, e.g., notebook computers, cell phones, personal data assistants (PDAs), etc.
Portable radio equipment such as notebook computers with wireless modems, cellular/cordless phones and other wireless devices are widely used in society. In wireless communication systems, geographic areas are often divided into cells. In each cell, mobile devices can communicate with a base unit in the cell via radio signals. In order to facilitate transmission and/or reception of signals, mobile devices in a wireless system often include an antenna.
For purposes of portability and customer appeal, portable equipment continues to shrink in size. There is a need for antennas suitable for use on portable equipment which are also small in size. In addition to being compact in size, an antenna on a portable device should be light in weight while having desired electrical characteristics such as resonance frequency, bandwidth, and gain.
Existing antennas often include a large number of parts making them complicated and/or difficult to assemble. Due to such complexity they can suffer from reliability problems. Antenna assembly difficulties and the use of a large number of parts can result in antennas that are relatively costly to manufacture.
In order to make portable radio equipment competitive from a cost standpoint, it is desirable to use a low cost antenna which is easy to assemble. The antennas should include relatively few parts, be capable of being manufactured in an automated manner and be reliable when used. Many wireless devices use a high-frequency band ranging from 700 to 2000 MHz. Accordingly, there is a need for a small, light, inexpensive antenna having good transmission and/or reception characteristics in all or a portion of at least the 700 to 2000 MHz frequency range. However, there is also a need for antennas that work well in other frequency bands.
The present invention is directed to an antenna structure for wireless devices, e.g., personal data assistants (PDAs) and notebook computers with wireless modems, cell phones, and other types of portable radio equipment.
In accordance with the present invention, antennas include an antenna arm and a conical spring radiating element attached to the antenna arm. In various embodiments, the conical radiating element may be protected by a cap and can be compressed to fit within the cap for storage. The antenna of the present invention may be inserted into a PC card for storage when not in use. The ability to compress the spring antenna for storage makes storage within a PC card possible.
In several embodiments, when the antenna is removed from the storage position, the antenna""s conical spring radiating element automatically extends as a result of the mechanical spring no longer being constrained by the walls of the PC card.
The antenna arm on which the antenna""s conical spring radiating element is mounted may be implemented as a layered circuit board. The spring radiating element is mounted on a first end of the layered circuit board. In some embodiments a middle layer of the circuit board includes a conductive element, e.g., a strip-line, for connecting the conical spring radiating element to a contact located at an opposite end of the antenna arm. The contact is used to couple the antenna to, e.g., receiver/transmitter circuitry.
In various embodiments, a secondary radiating element is incorporated into the antenna arm along an outside edge of the arm. At least a portion of the secondary radiating element remains exposed even when the antenna is placed into a storage position, e.g., inserted into a PC card. In various embodiments a portion of the secondary radiating element is used to couple the primary spring radiating element to the electrical contact used to connect the antenna arm to receiver/transmitter circuitry.
Antennas implemented in accordance with the present invention are simple to implement, have relatively few parts, are light and therefore tend to be well suited for use in mobile devices.
Numerous additional features, benefits and details of the methods and apparatus of the present invention are described in the detailed description which follows.